The aforementioned vibration exciters are known from the state of the art. They are used for generating a directed excitation vibration which can be introduced as alternating load impulses into the ground by way of suitable compaction means such as the tamping plates of a compaction device.
For this purpose, the vibration exciter comprises two unbalance shafts which extend in parallel with respect to each other, which are rotatable in opposite directions and on which at least one movable unbalance weight is arranged. The unbalance mass causes an excitation impulse in an excitation direction with a specific excitation amplitude during rotation of the shafts. This amplitude is directly linked to the compaction result during the excitation operation.
There may be a need, in the aforementioned vibration exciters, to change both the vibration amplitude by means of an adjustment of the amplitude and also the vector of said amplitude by means of a vector adjustment. The amplitude adjustment leads to a reduction in the vibration amplitude and consequently a reduction in the introduced load impulses, for example. The vector adjustment on the other hand causes a change in the direction of the vibration amplitude, so that a vibration tamper equipped with such a vibration exciter can be brought to forward and reverse operation, for example.
In order to perform an amplitude adjustment in the aforementioned “two-shaft exciter”, the movable unbalance masses are arranged on the unbalance shafts, which unbalance masses are movable relative to fixed unbalance masses on the unbalance shafts and are especially rotatable on the same. As a result of such a motion, the resulting total unbalance mass can be influenced in such a way that the resulting excitation amplitude will increase or decrease.
Such an apparatus is described, for example, by DE 102 41 200 A1, in which two unbalance shafts which are rotatable with respect to each other and extend in parallel are also arranged in a vibration tamper for generating a directed excitation vibration. Movable unbalance masses are arranged on the two shafts, which unbalance masses can be changed by an adjusting device in their position relative to fixed unbalance masses. The amplitude of the vibration exciter can be influenced in this manner.
Similar apparatuses are also described in DE 100 57 807 and DE 100 38 206.
The disadvantage of the vibration exciters known from the state of the art lies on the one hand in the complex configuration of an adjusting device for the adjustment of the movable unbalance masses on the two unbalance shafts, and on the other hand in the lack of an effective vector adjustment and the possibility to enable such a vector adjustment in a simple and technically reliable manner.